The present invention relates to an information system, and in particular to a local information system which may be used by pedestrians or as a vehicle information system. Such an information system may be arranged to provide data concerning local services, may allow local businesses to advertise or may advise the locally pertaining speed limits to the driver of a vehicle. The system may be used in some pedestrian environments, for instance airports or railway stations, to deliver relevant contextual information such as timetables, arrival and departure data and so on.
There have been proposals to crack down on speeding. There has even been a suggestion of zero tolerance of minor speed violations. In the United Kingdom, the Council for the Protection of Rural England is calling for a 40 mph speed limit on rural roads. Reductions in speed limits on roads are often largely ignored since drivers have become used to travelling on the road at the higher speed limit. Furthermore, local driving culture may be such that speed limits are generally ignored. In the UK for example, a great deal of motorway traffic travels at between 80 and 85 mph.
Police forces have already installed speed cameras in order that speeding motorists can be photographed and have points awarded to their licence or fines imposed without the need for intervention by a policeman. Conventional film based cameras have tended to have a margin of tolerance set into them in order that they only catch the worst offenders and thereby can be expected to have a reasonable lifetime before the film needs replacing. Film based cameras are slowly being replaced by digital cameras which do not have the same data storage problems. Furthermore, if the cameras have a telecommunications link then they are able to capture an image of every speeding vehicle that goes past them. If such cameras are set to a zero tolerance limit, it becomes entirely feasible for a driver committing only minor speeding offences to achieve sufficient speeding violations within a single journey to lose his license without him ever being aware of it.
Such a zero tolerance regime might result in many drivers spending a considerable amount of time looking at their speedometer and consequently less time looking at the road. Furthermore, excessively cautious drivers may drive at a larger margin below the actual speed limit causing unnecessary congestion, possibly frustration amongst other road users and even additional accidents.
For the rigid enforcement of speed limits, there are two numbers that the driver needs to know. These are what the local speed limit is, and the vehicle""s speed is. Whilst the UK has, in general, a reasonably good sign posting system, it is always possible to miss a road sign when the driver""s attention is directed elsewhere. This may be because of local traffic conditions requiring driver attention. Furthermore, it is not uncommon, especially on rural roads, for road signs to become obscured by overhanging trees in the summer or to appear as silhouettes when driving into bright sunlight. There has also been a tendency to increase the number of roadside signs, and this may increase further if roadside advertising or sign sponsorship is allowed, thus giving the driver far more peripheral and nonessential information to sift through before he can identify the local speed limit.
In the car, the speedometer is the most visible of instruments, but it is still provided in an instrument binnacle which requires the driver to avert his eyes from the road and to refocus on the distance to a few feet in front of him in order to read the vehicle""s speed. Often an experienced motorist knows his approximate speed by the sound of the engine of his car. Where some minor speeding is tolerated, this is a sufficiently accurate technique for a motorist to regulate his road speed. However, if a zero tolerance regime is enforced, then the motorist can no longer rely on this audio clue, and will be forced to examine his speedometer far more frequently and consequently be looking at the road less frequently.
According to a first aspect of the present invention, there is provided a vehicle information system comprising a receiver responsive to local data transmissions from roadside transmitters and an audio and/or visual communications device for communicating information to a vehicle""s occupant.
It is thus possible to provide an information system which is responsive to roadside transmitters in order to capture and hold data which may, for example be indicative of the local speed limit. Preferably the information system is arranged to receive broadcast data representative of at least a local speed limit. The information system, or some other vehicle system, can be arranged to compare this speed limit information with locally derived data representative of the vehicle""s speed and to indicate to the occupant, preferably the driver, the result of the comparison. Thus, for example, a warning may be issued to the driver if he is at or exceeding the speed limit. Additionally, an advisory warning may also be issued if the driver is close to the limit, for example in excess of 95% of the speed limit. Additionally or alternatively data representing the local speed limit may be provided to a vehicle""s engine management system or cruise control system so as to cause the vehicle to automatically stay within the speed limit until the driver intervenes to deliberately exceed the limit for example by switching the speed control system off or by xe2x80x9ckicking downxe2x80x9d the accelerator in a manner similar to that used to force a gear change in automatic vehicle boxes.
Preferably the receiver is a forward looking receiver. The receiver advantageously has a narrow acceptance aperture such that it is substantially responsive only to signals coming from an expected direction with respect to the vehicle. Thus if the receiver has a restricted acceptance aperture in the horizontal plane it can be arranged to receive data from roadside transmitters as the vehicle approaches them. The acceptance in the vertical plane may need to subtend nearly 90xc2x0 such that it can accept signals from transmitters mounted near the roadway or on buildings or on gantries extending over the road. In the UK, where vehicles travel on the left hand side of the carriageway, the receiver may be squinted to look towards the left to a position where traffic information signs are normally located. In other jurisdictions, the receiver""s antenna may have its primary lobe angled to the right.
Preferably the transmitter is arranged to transmit data representative of one or more of the local speed limit, distance to the next transmitter, emergency text messages, geographical data, transmitter identity data, local community data and advertisement data. This, list should not be considered exhaustive.
Advantageously, in a radio or microwave based system, only a limited number of radio channels or microwave channels would be required due to the limited transmission range associated with each transmitter. In a preferred embodiment of the invention only one transmission channel (frequency) is required. This has the advantage of simplifying manufacture of the vehicle information system and enable communication between parts of, or parties using, the system, i.e. car to roadside, roadside to car, police to car, police to roadside and so on. However transmissions from vehicles to the roadside could be on different frequencies to transmissions from the roadside to vehicles.
By providing data indicating the distance to the next transmitter, the system can perform an integral data validity check to estimate if the current speed limit is likely to be valid. Thus if the distance travelled from the last transmitter to the present location exceeds the distance indicated as being the valid distance to the next transmitter, the system can assert a signal to indicate that the speed limit data that it currently holds should not be considered as accurate and the driver can then act accordingly. Additionally, a road side transmitter may be arranged to transmit a plurality of distance validity messages. These messages may be associated with directional information which can be interpreted with the aid of an on board direction detection system, such as a compass. The messages may also be associated with transmitter identity codes. In an extension of such a system, the system might also transmit the distance to side roads or junctions in order that warnings might be issued upon approach to a side road or junction. Additionally, such a system may also transmit data concerning the speed limit pertaining on that side road such that the driver or vehicle systems are pre-warned.
Advantageously, the signal transmitted by the roadside transmitters also provides some form of direction indicating or carriageway coding signal in order to alleviate potential problems from multiple reflections. Consider a carriageway that runs north-south. A vehicle travelling north should expect to receive data only from those transmitters more northerly than it. The transmitters for a northerly travelling vehicle would, of course, be facing south. Similarly, vehicles travelling southwards would expect to receive data from northward facing transmitter. However there is a potential that as a southward travelling vehicle approaches a northward facing transmitter, radiation reflected from the southward travelling vehicle could then be propagated towards a vehicle travelling northwards. Such a vehicle could then be presented with wholly inaccurate data. In order to overcome this problem, a direction signal may be incorporated, for example a compass bearing or range of compass bearings, such that vehicles travelling in that approximate direction know that they can accept the data transmissions as being valid, whereas vehicles travelling outside of that range of directions ignore the transmissions. Additionally, or alternatively a lane identification signal may be transmitted such that vehicles travelling along one carriageway respond to one of the lane identification signals and ignore data carrying an alternative lane identification signal. Additionally or alternatively, each transmitter may transmit its own identity code and may also transmit the identity code or codes of the succeeding transmitter or transmitters. Thus the vehicle""s receiver is set up only to respond to the identity code of the next valid transmitter. In a variant of this system, each transmitter may transmit the identity codes of the adjacent transmitters of the neighbouring carriageway such that the vehicle is programmed to ignore transmissions emanating from those transmitters.
Capturing a transmitter identity code and associated positional information has further advantages. Given that the position of the transmitters are well known (because they are static objects for example affixed to road signs bridges or buildings) each transmitter can be correlated with its geographical position and acts as a way point. Vehicle navigation systems can then be programmed to navigate by reference to the transmitter identity codes. Such a system can be used as an adjunct to or alternative to GPS based systems. Advantageously the transmitters transmit their positional information in an explicit format. Thus for example each transmitter may transmit its latitude and longitude in a word such as:
 less than NAVWGS, LAT=51, 35.005N, LONG=05, 12.345W greater than 
where:
NAV indicates that positional information follows
WGS identifies the format of the information:
LAT=latitude
LONG=longitude.
Alternatively, where local mapping authorities have developed their own alternatives for specifying positions these can be used. Thus an alternative word might be:
 less than NAVUKMAPOS, SU987123 greater than 
where:
UKMAPOS specifies the coordinate system used on the ordnance survey maps in the UK,
SU specifies the map area and the final 6 digits is a standard 6 digit positional reference.
As a further alternative, positional data may be given in a human readable form, for example:
 less than NAVTEXT, Passing through Kenton, South on A379 greater than 
Navigational systems based on the transmitter identity codes or explicit position data can be expected to outperform GPS based systems in urban areas where a GPS receiver may not be able to view sufficient GPS satellites simultaneously in order to calculate its position. Furthermore, GPS needs a digital map to convert its information into usable navigation data, and will fail in tunnels and intermittently in built up areas.
In contrast, urban areas are normally densely populated with sign posts so that the local transmitters can be arranged at frequent intervals.
Preferably a facility is also provided for local authorities and emergency services to add messages. Thus the police could introduce local speed limits in response to adverse road conditions or accidents. Similarly, a local authority and the community could piggyback local information into the system and traders could advertise their presence to passing motorists. The information that the transmitter is to transmit may be stored in a local memory, that is cached, and can be periodically updated.
Preferably the vehicle""s information system also includes the transmitter. The transmitter may be used to identify the vehicle to the roadside receiver as the vehicle passes it. The or each roadside transmitter receiver unit may then be arranged to pass vehicle identity information or other data into a telecommunications network. Such a system may be used by fleet operators in order to track the location of their vehicles. Additionally or alternatively, security companies may also use it to track delivery vehicles or stolen vehicles. In a further extension of the system, once a stolen vehicle has been located, adjacent roadside transmitters may be arranged to transmit a disable code targeted at that vehicle in order to cause the vehicle""s engine management system or other system to limit the vehicle speed or to shut it down completely. Advantageously the retransmit feature and response to certain instructions can be wholly or partially disabled under control of the driver, although deactivation may require the use of security means, such as passwords.
The system may also be used for automatic road tolling or controlled access to roads or spaces, such as car parks.
The system might further be used as an alarm, with a driver operated panic button being located within the passenger compartment. Thus the driver may activate a panic button to assert an emergency signal in those situations where the driver feels worried or intimidated, but nevertheless wishes to keep the vehicle moving, for example a road rage incident. A further panic button, or an output from a vehicle monitoring system such as an engine management system, deceleration sensor or air bag activation system, may be used to initiate an emergency broadcast message if the user or an automated system deems it appropriate.
Such a system may further be adapted to automatically transmit to the authorities when a speed violation above a certain threshold has occurred. Thus there is potential for a vehicle fitted with the system to automatically inform the authorities when the driver is speeding.
Preferably the data links between the roadside transmitter and the car are infrared or microwave links as these can be arranged to give line of sight coverage, thereby providing only local coverage. However, it is expected that microwave technology would be preferred as this has the potential to function in the mornings and the evenings when the sun is low at the horizon and might otherwise wash out infrared communication links.
Additionally or alternatively, magnetic data links may be provided. Thus transmission coils may be embedded adjacent to the road or in the road surface in order that vehicles can communicate with the coils as they pass over or adjacent them.
Advantageously a vehicle fitted with the system may also have a rear facing transmitter in order that it can transmit messages to a vehicle following it. Such a system may be used to daisy chain messages. Additionally or alternatively, the system may be used to enhance road safety. For example, a car fitted with the system may also include an accelerometer or other system able to judge when the car is undergoing severe braking, as might incur in an emergency situation. A message indicative of this may then be transmitted to following cars in order that the drivers can be alerted promptly or that in-car systems take control of the following vehicles and automatically decelerate them in order to reduce the chances of an impact.
Advantageously, each transmitter may be arranged to have a quiescent mode in which it transmits a carrier signal, possibly in association with other data, and vehicles and road side units can use the Doppler shift of the signal to estimate the vehicle""s speed and/or relative speed. This speed data, and rate of change of speed data may be used to judge when a vehicle is speeding and/or undergoing rapid deceleration. Advantageously forward facing transmitters are distinguished from rear facing transmitters by identity codes thereby enabling an on board data processor to distinguish between signals from vehicles travelling in the same direction and those travelling in the opposite direction. The carrier signal may be transmitted continuously, or discontinuously but frequently.
The transmitter may also act in a RADAR mode, using microwave travel time to a vehicle and back to provide an estimate of range. The signals may be positively returned from vehicles, i.e. reflected, or actively retransmitted with data identifying the propagation delay introduced by the transmitter and receiver of the vehicle actively returning the signal.
According to a second aspect of the present invention, there is provided a roadside transmitter for use in association with a in-vehicle data system, the transmitter being arranged to transmit local road data to passing vehicles.
Advantageously a receiver is also provided, optionally in the road side transmitter, for receiving data transmitted from passing vehicles. Preferably the road side transmitter and receiver are associated with a controller which is also connected to a telecommunications network for exchanging data with a remote site.
According to a third aspect of the present invention there is provided a local area information system, comprising data transmitters having a memory for storing information relating to the local area and a plurality of user devices for receiving data from the transmitters and presenting the information to a user.
According to a fourth aspect of the present invention there is provided a transmitter for a local area information service, the transmitter comprising at least one of a microwave, radio, or ultrasonic or infrared transmission device, and a memory for storing information, said information by repeatedly retransmitted by the transmission device.
According to a fifth aspect of the present invention, there is provided a receiver responsive to data transmissions from local transmitters, and for storing the information in a local memory such that a user can select the information for presentation to the user.
It is thus possible to provide a information system which can provide information pertaining to the local area to a user. In particular the information may include advertisements from local shops or national brand owners.
The local transmitters may be in the form of posts or small transmitters attached to buildings or street furniture. Thus the information could be transmitted into a very small cell indeed, perhaps only of the order of 10""s of meters across.
Advantageously the receiver constituting an embodiment of the present invention comprises a display device in co-operation with a local data processor. Indeed the receiver may comprise a portable computing device, such as a personal digital assistant or palmtop computer. Such a device can function in a pedestrian environment, and may also be used within the automotive environment.
Thus a single receiver or display device thereof can constitute a common component in an embodiment of the receiver according to the first aspect of the present invention and of the fifth aspect.
Indeed, it is expected that a device such as a small computer, personal digital assistant or the like may be used in a docking station when in a vehicle so as to receive data from the in vehicle receiver or transponder and to display it to the occupants of the vehicle. However, the same device may be removed from its docking station and use an inbuilt receiver or infrared port, or dock with portable receiver or transponder module, to allow information to be delivered in a pedestrian environment, such as shopping complexes, airports, bus stations, train stations, hotels, streets and the like.
The high data rates that can be supported in the local regions around each transmitter enables a vast amount of data to be transmitted to the receiver very quickly. Thus a user can quickly receive the data about product prices or promotions offered by a business. The data may be organised in a book like or other browsable form such that the user can sift through the information to select those portions of interest.
Preferably the receiver can also transmit data to the local area transmitters, and these are connected to a communication system such that enquiries can be made concerning information not stored in the memory of the local transmitter, but such that the information can be accessed via a broader network of computers. Thus a user is able to access data across, for example, the Internet.
Preferably the receiver""s bidirectional communication link with the local area transmitters has sufficient bandwidth to support voice communication either in place of or simultaneously with data and/or video transmission. Thus the hand held receiver can act to accept data from the local transmitter for which the recipient need not pay, and also make use of more specific services such as internet access, voice or videophone for which the user may pay or may not pay.
Thus a receiver constituting an embodiment of the present invention may provide the functionality of the WAP mobile telephone. However, whereas a WAP telephone user has to dial out to browse the internet to obtain data such as local restaurant menus, bus time tables and so, the present invention makes that information continuously available from the local transmitters.
The information may be categorised by topic using embedded tags, such as meta tags, which may be used to present data to the user in a structured manner. Since the memory capacity of the local transmitter may be larger than that of the receiver unit, the receiver may conserve its memory resource by capturing only portions of the data, such selection being done on the basis of the embedded tags. The high repetition rate of data transmission from the local transmitter ensures that the data which was not captured will be available without a significant delay should the user become interested in it.
According to a sixth aspect of the present invention, there is provided a method of making data available to at least one user, the method comprising the steps of holding data in a memory within a transmitter arranged to transmit data in a region surrounding the transmitter; and repeatedly transmitting the data held in the memory into the region such that a suitable receiver within the region can make the data available to a user.
Preferably the data is categorised such that it is presented in a sortable or indexed format.
Preferably the data includes advertisements.
Preferably the advertisers pay for advertising xe2x80x9cspacexe2x80x9d so as to subsidise, or render free, the cost to the user for receiving some or all of the data transmitted from the transmitter.